An aortic graft is an endovascular prosthesis for placement in the aorta, in a weakened area, such as an aneurysm or an aortic dissection. An aortic aneurysm is an abnormal dilation or enlargement of the arterial wall of the aorta. If a significantly large aneurysm is not treated, it can rupture with abrupt fatal blood loss, either into the abdominal or thoracic cavity of the patient.
An aortic graft is typically made of a tube of pliable material provided with a stent for anchoring the graft in its intended position within the blood vessel by exerting an outwardly directed radial pressure against the surrounding aortic wall. This requires in the region of the stent a relatively healthy aortic wall that can withstand the radial pressure for years. Patients diagnosed with aortic aneurysms are often in poor health due to other illnesses which increase the risk of complications associated with an operation. Most prior art stent grafts are designed for abdominal aortic aneurysms (AAA) involving the pararenal and the infrarenal aorta. Examples of such grafts are described in U.S. Pat. Nos. 5,984,955 and 6,016,810. Many of these grafts are bifurcated and extend to the iliac arteries. Aortic grafts of these types can typically be placed using transluminal, minimally invasive, procedures where the grafts are percutaneously introduced via a femoral puncture site, and the entire procedure can be performed using local anaesthesia.
With respect to aortic grafts for the repair of thoracoabdominal aortic aneurysms (aneurysms in the descending thoracic aorta) and other thoracic aortic aneurysms (aneurysms in the ascending thoracic aorta including the aortic arch) only a few proposals for minimally invasive procedures have been made.
U.S. Pat. No. 6,099,548 proposes to advance the graft into the ascending thoracic aorta and to lock it to the aortic wall by expanding a stent in the proximal end of the graft. However, adjacent the heart the flow rate of blood through the aorta is so high that the risk of dislocation of the proximal stent is considerable.
In a particular lethal kind of aortic aneurysm the aortic wall is dissected to form a bogus lumen that establishes a parallel flow path for blood. The only method of repair is open surgery. In a so-called elephant trunk procedure, a stented distal end of a secondary graft pad is fixed in the descending aorta, and the proximal end of the secondary graft part is sutured to a primary graft part that is placed in the ascending aorta and anastomosed to the branch arteries carotis communis, subclavia and truncus brachiocephalicus.
During the operation the patient is subjected to cardiac arrest and systemic circulatory arrest, and although the patient has been cooled to a very low body temperature, such as 16° C. and selective cerebral perfusion is performed, the duration of the operation is a critical factor.
Dissections of the type in which the ascending aorta is involved pose a particular problem. With prior art techniques the mortality rate is 75% within 24 hours of initiation of the condition and 90% within one week. The surgeon thus has an extremely short time to prepare and perform surgery.
U.S. Pat. No. 6,773,457 discloses an aortic graft device which includes a graft portion and a corrugated or elephant trunk portion integral with and extending from the graft portion. The device is designed to be fitted to the aorta descendens. The corrugated portion, when fitted to a patient, forms the ascending portion of the device and is able to flex to the shape of the ascending aortic section in which it is placed. The device is fixed in place by locating it into the patient's previously opened aorta while the elephant trunk is averted into the graft portion. The surgeon sutures the rounded edge at the fold to the aortic wall, after which the trunk is fully unfolded. A problem with this procedure is that a surgeon has difficulties in suturing as a result of the fact that the rounded edge is thin, limp and lacks springiness. As a result of this, the suturing operation can take longer than necessary, which is undesirable and potentially dangerous.
French Patent Application number 2,777,450 discloses a stent graft which is provided with an elephant trunk and fixing mechanisms at both ends of the device. The upper end of the stent graft section is provided with an annular fixing band therearound which is fixed to a lumen-external band by rivets or sutures. The elephant trunk can be fixed to the lumen wall by suturing. The device disclosed in this document is not intended for location in the aorta descendens and is fitted in a different manner to the manner of fitting of the device of U.S. Pat. No. 6,773,457 discussed above.